Many electrical devices such as cell phones, personal digital assistants (PDAs), laptops, etc. are powered by a source of relatively low-voltage DC power. Because power is generally delivered through a wall outlet as high-voltage AC power, a device, typically referred to as a power converter, is required to transform the high-voltage AC power to a low-voltage DC power, so as to provide output voltages and currents that meet the requirements of the electrical devices.
In operation, a power converter may use a controller to regulate output power delivered to the electrical device (i.e., load), and the power is regulated generally by controlling the ON and OFF states of a power switch in the power converter through the controller. In the power converter application, every external component has its maximum allowable current, voltage and power rating, and therefore the output power limit is required for protecting all components in safe operation region.